Human Pancreatic Islets React to Glucolipotoxicity by Secreting Pyruvate and Citrate

Progressive decline in pancreatic beta-cell function is central to the pathogenesis of type 2 diabetes (T2D). Here, we explore the relationship between the beta cell and its nutritional environment, asking how an excess of energy substrate leads to altered energy production and subsequent insulin secretion. Alterations in intracellular metabolic homeostasis are key markers of islets with T2D, but changes in cellular metabolite exchanges with their environment remain unknown. We answered this question using nuclear magnetic resonance-based quantitative metabolomics and evaluated the consumption or secretion of 31 extracellular metabolites from healthy and T2D human islets. Islets were also cultured under high levels of glucose and/or palmitate to induce gluco-, lipo-, and glucolipotoxicity. Biochemical analyses revealed drastic alterations in the pyruvate and citrate pathways, which appear to be associated with mitochondrial oxoglutarate dehydrogenase (OGDH) downregulation. We repeated these manipulations on the rat insulinoma-derived beta-pancreatic cell line (INS-1E). Our results highlight an OGDH downregulation with a clear effect on the pyruvate and citrate pathways. However, citrate is directed to lipogenesis in the INS-1E cells instead of being secreted as in human islets. Our results demonstrate the ability of metabolomic approaches performed on culture media to easily discriminate T2D from healthy and functional islets.

CRISPR/Cas9-mediated inactivation of the phosphatase activity of soluble epoxide hydrolase prevents obesity and cardiac ischemic injury

INTRODUCTION

Although the physiological role of the C-terminal hydrolase domain of the soluble epoxide hydrolase (sEH-H) is well investigated, the function of its N-terminal phosphatase activity (sEH-P) remains unknown.

OBJECTIVES

This study aimed to assess in vivo the physiological role of sEH-P.

METHODS

CRISPR/Cas9 was used to generate a novel knock-in (KI) rat line lacking the sEH-P activity.

RESULTS

The sEH-P KI rats has a decreased metabolism of lysophosphatidic acids to monoacyglycerols. KI rats grew almost normally but with less weight and fat mass gain while insulin sensitivity was increased compared to wild-type rats. This lean phenotype was more marked in males than in female KI rats and mainly due to decreased food consumption and enhanced energy expenditure. In fact, sEH-P KI rats had an increased lipolysis allowing to supply fatty acids as fuel to potentiate brown adipose thermogenesis under resting condition and upon cold exposure. The potentiation of thermogenesis was abolished when blocking PPARγ, a nuclear receptor activated by intracellular lysophosphatidic acids, but also when inhibiting simultaneously sEH-H, showing a functional interaction between the two domains. Furthermore, sEH-P KI rats fed a high-fat diet did not gain as much weight as the wild-type rats, did not have increased fat mass and did not develop insulin resistance or hepatic steatosis. In addition, sEH-P KI rats exhibited enhanced basal cardiac mitochondrial activity associated with an enhanced left ventricular contractility and were protected against cardiac ischemia-reperfusion injury.

CONCLUSION

Our study reveals that sEH-P is a key player in energy and fat metabolism and contributes together with sEH-H to the regulation of cardiometabolic homeostasis. The development of pharmacological inhibitors of sEH-P appears of crucial importance to evaluate the interest of this promising therapeutic strategy in the management of obesity and cardiac ischemic complications.

Role of mitochondria-associated endoplasmic reticulum membrane (MAMs) interactions and calcium exchange in the development of type 2 diabetes

Glucotoxicity-induced β-cell dysfunction in type 2 diabetes is associated with alterations of mitochondria and the endoplasmic reticulum (ER). Mitochondria and ER form a network in cells that controls cell function and fate. Mitochondria of the pancreatic β cell play a central role in the secretion of insulin in response to glucose through their ability to produce ATP. Both organelles interact at contact sites, defined as mitochondria-associated membranes (MAMs), which were recently implicated in the regulation of glucose homeostasis. Here, we review MAM functions in the cell and we focus on the crosstalk between the ER and Mitochondria in the context of T2D, highlighting the pivotal role played by MAMs especially in β cells through inter-organelle calcium exchange and glucotoxicity-associated β cell dysfunction.

Fast and ergonomic extraction of adherent mammalian cells for NMR-based metabolomics studies

Cellular metabolomics has become key to elucidate mechanistic aspects in various fields such as cancerology or pharmacology, and is rapidly becoming a standard phenotyping tool accessible to the broad biological community. Acquisition of reliable spectroscopic datasets, such as nuclear magnetic resonance (NMR) spectra, to characterize biological systems depends on the elaboration of robust methods for cellular metabolites extraction. Previous studies have addressed many issues raised by these protocols, however with little pondering on ergonomic and practical aspects of the methods that impact their scalability, reproducibility and hence their suitability to high-throughput studies or their use by non-metabolomics experts. Here, we optimize a fast and ergonomic protocol for extraction of metabolites from adherent mammalian cells for NMR metabolomics studies. The proposed extraction protocol, including cell washing, metabolism quenching and actual extraction of intracellular metabolites, was first optimized on HeLa cells. Efficiency of the protocol, in its globality and for the different individual steps, was assessed by NMR quantification of 27 metabolites from cellular extracts. We show that a single PBS wash provides a seemly compromise between contamination from growth medium and leakage of intracellular metabolites. In HeLa cells, extraction using pure methanol, without cell scraping, recovered a higher amount of intracellular metabolites than the reference methanol/water/chloroform method with cell scraping, with yields varying across metabolite classes. Optimized and reference protocols were further tested on eight cell lines of miscellaneous nature, and inter-operator reproducibility was demonstrated. Our results stress the need for tailored extraction protocols and show that fast protocols minimizing time-consuming steps, without compromising extraction yields, are suitable for high-throughput metabolomics studies. Graphical abstract.

Differential Effect of Glucose on ER-Mitochondria Ca2+ Exchange Participates in Insulin Secretion and Glucotoxicity-Mediated Dysfunction of β-Cells

Glucotoxicity-induced β-cell dysfunction in type 2 diabetes is associated with alterations of mitochondria and the endoplasmic reticulum (ER). Both organelles interact at contact sites, defined as mitochondria-associated membranes (MAMs), which were recently implicated in the regulation of glucose homeostasis. The role of MAMs in β-cells is still largely unknown, and their implication in glucotoxicity-associated β-cell dysfunction remains to be defined. Here, we report that acute glucose treatment stimulated ER-mitochondria interactions and calcium (Ca²⁺) exchange in INS-1E cells, whereas disruption of MAMs altered glucose-stimulated insulin secretion (GSIS). Conversely, chronic incubations with high glucose of either INS-1E cells or human pancreatic islets altered GSIS and concomitantly reduced ER Ca²⁺ store, increased basal mitochondrial Ca²⁺, and reduced ATP-stimulated ER-mitochondria Ca²⁺ exchanges, despite an increase of organelle interactions. Furthermore, glucotoxicity-induced perturbations of Ca²⁺ signaling are associated with ER stress, altered mitochondrial respiration, and mitochondria fragmentation, and these organelle stresses may participate in increased organelle tethering as a protective mechanism. Last, sustained induction of ER-mitochondria interactions using a linker reduced organelle Ca²⁺ exchange, induced mitochondrial fission, and altered GSIS. Therefore, dynamic organelle coupling participates in GSIS in β-cells, and over time, disruption of organelle Ca²⁺ exchange might be a novel mechanism contributing to glucotoxicity-induced β-cell dysfunction.

Reduction of endoplasmic reticulum- mitochondria interactions in beta cells from patients with type 2 diabetes

Type 2 diabetes develops when beta cells are not able to fulfill insulin needs. The role of the endoplasmic reticulum-mitochondria junction in coordinating the functions of these two organelles throughout the natural history of type 2 diabetes is determinant and may explain the alterations of insulin biosynthesis. Our goal was to study endoplasmic reticulum and mitochondrial interactions in human beta cells from organ donors with type 2 diabetes. Pancreas samples were obtained via the network for pancreatic organ donors with diabetes (nPOD) based on disease status with 12 subjects with type 2 diabetes and 9 non-diabetic controls. We examined pancreatic specimens by immunofluorescence, in situ hybridization and in situ proximity ligation assay and compared the results to an in vitro model of beta-cell dysfunction. Expression of proteins that enable tethering and exchanges between endoplasmic reticulum (ER) and mitochondria and quantification of interconnection through mitochondria associated membranes (MAM) was investigated. In beta cells from type 2 diabetic cases as compared to controls, there was a significant increase in reticular expression of inositol triphosphate receptor-2 (IP3R2) both at the protein and mRNA levels, no difference in mitochondrial transit peptide receptor TOM20 and mitofusin-2 expressions, and a decrease in the expression of voltage-dependent anion channel-1 (VDAC-1). The number of IP3R2-VDAC-1 complexes identified by in situ proximity ligation assay was significantly lower in diabetic islets and in beta cells of diabetics as compared to controls. Treatment of Min6-B1 cells with palmitate altered glucose-stimulated insulin secretion, increased ER stress and significantly reduced ER-mitochondrial interactions. We can conclude that specific changes in reticular and mitochondrial beta cell proteins characterize human type 2 diabetes with reduction in organelle interactions. This finding opens new targets of intervention.

miRNA-375 a Sensor of Glucotoxicity Is Altered in the Serum of Children with Newly Diagnosed Type 1 Diabetes

Background. The use of miRNAs as biomarkers for Type 1 Diabetes (T1D) risk is attractive as T1D is usually diagnosed in front of acute symptoms. As miR-375 is highly expressed in the endocrine pancreas, we postulated that its circulating level might reflect beta cell alterations and might be altered in the blood of T1D patients recently diagnosed. Methods. Sera were obtained from 22 T1D children at onset of the disease, before subcutaneous insulin treatment, and from 10 nondiabetic pediatric controls. MiR-375 seric level was quantified by stem-loop RT-PCR-based assay. MiRNAs regulations in isolated human islets in response to high glucose concentrations were determined by TaqMan Low-Density Array. Results. The abundance of miR-375, among the 410 miRNAs detected in human islets, mirrored its well-established role in rodent islet biology. Upregulated miRNAs targeted genes involved in islet homeostasis and regulation of beta cell mass. Downregulated miRNAs, including miR-375, were involved in pancreas secretion and protein turnover. Seric level of miR-375 was lower in T1D children versus age-matched controls, without any correlations with HbA1c, glycaemia, and number of autoantibodies. Conclusion. Altered circulating level of miR-375 at onset of T1D might be a general biomarker of metabolic alterations and inflammation associated with the disease.

Adipose Tissue-Derived Stem Cells From Obese Subjects Contribute to Inflammation and Reduced Insulin Response in Adipocytes Through Differential Regulation of the Th1/Th17 Balance and Monocyte Activation

Obesity, through low-grade inflammation, can drive insulin resistance and type 2 diabetes. While infiltration of adipose tissue (AT) with mononuclear cells (MNCs) is well established in obesity, the functional consequences of these interactions are less understood. Herein, we cocultured human adipose-derived stem cells (ASCs) from obese individuals with MNCs and analyzed their reciprocal behavior. Presence of ASCs 1) enhanced interleukin (IL)-17A secretion by Th17 cells, 2) inhibited γ-interferon and tumor necrosis factor α secretion by Th1 cells, and 3) increased monocyte-mediated IL-1β secretion. IL-17A secretion also occurred in stromal vascular fractions issued from obese but not lean individuals. Th17 polarization mostly depended on physical contacts between ASCs and MNCs-with a contribution of intracellular adhesion molecule-1-and occurred through activation of the inflammasome and phosphatidylinositol 3-kinase pathways. ASCs favored STAT3 over STAT5 transcription factor binding on STAT binding sites within the IL-17A/F gene locus. Finally, conditioned media from activated ASC-MNC cocultures inhibited adipocyte differentiation mRNA markers and impaired insulin-mediated Akt phosphorylation and lipolysis inhibition. In conclusion, we report that obese- but not lean-derived ASCs induce Th17 promotion and monocyte activation. This proinflammatory environment, in turn, inhibits adipogenesis and adipocyte insulin response. The demonstration of an ASC-Th17-monocyte cell axis reveals a novel proinflammatory process taking place in AT during obesity and defines novel putative therapeutic targets.

Imeglimin normalizes glucose tolerance and insulin sensitivity and improves mitochondrial function in liver of a high-fat, high-sucrose diet mice model

Imeglimin is the first in a new class of oral glucose-lowering agents currently in phase 2b development. Although imeglimin improves insulin sensitivity in humans, the molecular mechanisms are unknown. This study used a model of 16-week high-fat, high-sucrose diet (HFHSD) mice to characterize its antidiabetic effects. Six-week imeglimin treatment significantly decreased glycemia, restored normal glucose tolerance, and improved insulin sensitivity without modifying organs, body weights, and food intake. This was associated with an increase in insulin-stimulated protein kinase B phosphorylation in the liver and muscle. In liver mitochondria, imeglimin redirects substrate flows in favor of complex II, as illustrated by increased respiration with succinate and by the restoration of respiration with glutamate/malate back to control levels. In addition, imeglimin inhibits complex I and restores complex III activities, suggesting an increase in fatty acid oxidation, which is supported by an increase in hepatic 3-hydroxyacetyl-CoA dehydrogenase activity and acylcarnitine profile and the reduction of liver steatosis. Imeglimin also reduces reactive oxygen species production and increases mitochondrial DNA. Finally, imeglimin effects on mitochondrial phospholipid composition could participate in the benefit of imeglimin on mitochondrial function. In conclusion, imeglimin normalizes glucose tolerance and insulin sensitivity by preserving mitochondrial function from oxidative stress and favoring lipid oxidation in liver of HFHSD mice.

Optimized purification strategies for the elimination of non-specific products in the isolation of GAD65-specific monoclonal autoantibodies

Autoantibodies against antigens expressed by insulin-producing β cells are circulating in both healthy individuals and patients at risk of developing Type 1 diabetes. Recent studies suggest that another set of antibodies (anti-idiotypic antibodies) exists in this antibody/antigen interacting network to regulate auto-reactive responses. Anti-idiotypic antibodies may block the antigen-binding site of autoantibodies or inhibit autoantibody expression and secretion. The equilibrium between autoantibodies and anti-idiotypic antibodies plays a critical role in mediating or preventing autoimmunity. In order to investigate the molecular mechanisms underlying such a network in autoimmunity and potentially develop neutralizing reagents to prevent or treat Type 1 diabetes, we need to produce autoantibodies and autoantigens with high quality and purity. Herein, using GAD65/anti-GAD65 autoantibodies as a model system, we aimed to establish reliable approaches for the preparation of highly pure autoantibodies suitable for downstream investigation.

Soluble epoxide hydrolase inhibition improves coronary endothelial function and prevents the development of cardiac alterations in obese insulin-resistant mice

This study addressed the hypothesis that inhibiting the soluble epoxide hydrolase (sEH)-mediated degradation of epoxy-fatty acids, notably epoxyeicosatrienoic acids, has an additional impact against cardiovascular damage in insulin resistance, beyond its previously demonstrated beneficial effect on glucose homeostasis. The cardiovascular and metabolic effects of the sEH inhibitor trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB; 10 mg/l in drinking water) were compared with those of the sulfonylurea glibenclamide (80 mg/l), both administered for 8 wk in FVB mice subjected to a high-fat diet (HFD; 60% fat) for 16 wk. Mice on control chow diet (10% fat) and nontreated HFD mice served as controls. Glibenclamide and t-AUCB similarly prevented the increased fasting glycemia in HFD mice, but only t-AUCB improved glucose tolerance and decreased gluconeogenesis, without modifying weight gain. Moreover, t-AUCB reduced adipose tissue inflammation, plasma free fatty acids, and LDL cholesterol and prevented hepatic steatosis. Furthermore, only the sEH inhibitor improved endothelium-dependent relaxations to acetylcholine, assessed by myography in isolated coronary arteries. This improvement was related to a restoration of epoxyeicosatrienoic acid and nitric oxide pathways, as shown by the increased inhibitory effects of the nitric oxide synthase and cytochrome P-450 epoxygenase inhibitors l-NA and MSPPOH on these relaxations. Moreover, t-AUCB decreased cardiac hypertrophy, fibrosis, and inflammation and improved diastolic function, as demonstrated by the increased E/A ratio (echocardiography) and decreased slope of the end-diastolic pressure-volume relation (invasive hemodynamics). These results demonstrate that sEH inhibition improves coronary endothelial function and prevents cardiac remodeling and diastolic dysfunction in obese insulin-resistant mice.

The MHC class II cofactor HLA-DM interacts with Ig in B cells

B cells internalize extracellular Ag into endosomes using the Ig component of the BCR. In endosomes, Ag-derived peptides are loaded onto MHC class II proteins. How these pathways intersect remains unclear. We find that HLA-DM (DM), a catalyst for MHC class II peptide loading, coprecipitates with Ig in lysates from human tonsillar B cells and B cell lines. The molecules in the Ig/DM complexes have mature glycans, and the complexes colocalize with endosomal markers in intact cells. A larger fraction of Ig precipitates with DM after BCR crosslinking, implying that complexes can form when DM meets endocytosed Ig. In vitro, in the endosomal pH range, soluble DM directly binds the Ig Fab domain and increases levels of free Ag released from immune complexes. Taken together, these results argue that DM and Ig intersect in the endocytic pathway of B cells with potential functional consequences.

Paramagnetic nanoparticles to track and quantify in vivo immune human therapeutic cells

This study aims to investigate gadolinium-based nanoparticles (Gd-HNP) for in vitro labeling of human plasmacytoid dendritic cells (HuPDC) to allow for in vivo tracking and HuPDC quantifying using magnetic resonance imaging (MRI) following parenteral injection. Human plasmacytoid DC were labeled (LabHuPDC) with fluorescent Gd-HNP (Gd-FITC-HNP) and injected via intraperitoneal and intravenous routes in 4-5 NOD-SCID β2m(-/-)mice (treated mice = TM). Control mice (CM) were similarly injected with unlabeled HuPDC. In vivo 7 T MRI was performed 24 h later and all spleens were removed in order to measure Gd and fluorescence contents and identify HuPDC. Gd-FITC-HNP efficiently labeled HuPDC (0.05 to 0.1 pg per cell), without altering viability and activation properties. The magnetic resonance (MR) signal was exclusively due to HuPDC. The normalized MR splenic intensity for TM was significantly higher than for CM (p < 0.024), and highly correlated with the spleen Gd content (r = 0.97), and the number of HuPDC found in the spleen (r = 0.94). Gd-FITC-HNP allowed for in vivo tracking and HuPDC quantifying by means of MRI following parenteral injection, with very high sensitivity (<3000 cells per mm(3)). The safety of these new nanoparticle types must be confirmed via extensive toxicology tests including in vivo stability and biodistribution studies.

Losartan, an angiotensin II type 1 receptor blocker, protects human islets from glucotoxicity through the phospholipase C pathway

As shown in a large clinical prospective trial, inhibition of the renin-angiotensin system (RAS) can delay the onset of type 2 diabetes in high-risk individuals. We evaluated the beneficial effects of RAS inhibition on β-cell function under glucotoxic conditions. Human islets from 13 donors were cultured in 5.5 mM (controls) or 16.7 mM glucose [high glucose (HG)] for 4 d with or without losartan (5 μM), a selective AT1R blocker, and/or U73122 (2 μM), a selective PLC inhibitor, during the last 2 d. HG induced RAS activation with overexpression of AT1R (P<0.05) and angiotensinogen (P<0.001) mRNAs. HG increased endoplasmic reticulum (ER) stress markers (P<0.001) such as GRP78, sXBP1, and ATF4 mRNAs and Grp78 protein levels (P<0.01). HG also decreased reticular calcium concentration (P<0.0001) and modified protein expressions of ER calcium pumps with reduction of SERCA2b (P<0.01) and increase of IP3R2 (P<0.05). Losartan prevented these deleterious effects and was associated with improved insulin secretion despite HG exposure. AT1R activation triggers the PLC-IP3-calcium pathway. Losartan prevented the increase of PLC β1 and γ1 protein levels induced by HG (P<0.05). U73122 reproduced all the protective effects of losartan. AT1R blockade protects human islets from the deleterious effects of glucose through inhibition of the PLC-IP3-calcium pathway.

Glucose inhibits angiogenesis of isolated human pancreatic islets

Owing to strong interactions between pancreatic islets and the surrounding capillary network, we hypothesized that high glucose concentrations might affect key angiogenesis factors from isolated human islets, thus contributing to beta-cell failure in diabetes. Human islets from eight distinct donors were studied following 96 h in culture in the presence of normal (5.5 mmol/l) or high (16.7 mmol/l) glucose concentrations. Similar studies were performed with HUVECs. Human angiogenesis-related genes and corresponding proteins were studied by real-time quantitative PCR (RT-qPCR) and protein arrays respectively. Angiogenesis and proliferation assays were also performed with HUVECs under the same culture conditions. RT-qPCR and proteome analysis of human islets incubated with 16.7 mM/l glucose revealed a significant decrease in pro-angiogenic factors including vascular endothelial growth factor (VEGF) mRNA by 20% and VEGF protein levels by 42% as well as additional proteins such as fibroblast growth factor-4 by 41%, MMP9 by 18%, monocyte chemoattractant protein-1 by 21%, and prolactin by 25%. In contrast, we observed a 17% increase in thrombospondin-1 (TSP-1, listed as THBS1 in the HUGO database) and a 37% increase in angiotensinogen gene expression levels, but neither angiotensin-converting enzyme nor angiotensin II type 1 receptor gene expression was affected. The amounts of anti-angiogenic proteins such as TSP-1 and serpin B5/maspin were also increased by 70 and 98% respectively as well as endostatin by 63%. Angiogenesis assays of HUVECS in the presence of high glucose concentrations revealed a 30% decrease in tree-like tubular network formation. These data suggest that glucose reduces key factors of islet angiogenesis, which might exacerbate beta-cell failure.

Mesenchymal stem cells protect NOD mice from diabetes by inducing regulatory T cells

AIMS/HYPOTHESIS

Displaying immunomodulatory capacities, mesenchymal stem cells (MSCs) are considered as beneficial agents for autoimmune diseases. The aim of this study was to examine the ability of MSCs to prevent autoimmune diabetes in the NOD mouse model.

METHODS

Prevention of spontaneous insulitis or of diabetes was evaluated after a single i.v. injection of MSCs in 4-week-old female NOD mice, or following the co-injection of MSCs and diabetogenic T cells in irradiated male NOD recipients, respectively. The frequency of CD4(+)FOXP3(+) cells and Foxp3 mRNA levels in the spleen of male NOD recipients were also quantified. In vivo cell homing was assessed by monitoring 5,6-carboxyfluorescein diacetate succinimidyl ester (CFSE)-labelled T cells or MSCs. In vitro, cell proliferation and cytokine production were assessed by adding graded doses of irradiated MSCs to insulin B9-23 peptide-specific T cell lines in the presence of irradiated splenocytes pulsed with the peptide.

RESULTS

MSCs reduced the capacity of diabetogenic T cells to infiltrate pancreatic islets and to transfer diabetes. This protective effect was not associated with the modification of diabetogenic T cell homing, but correlated with a preferential migration of MSCs to pancreatic lymph nodes. While injection of diabetogenic T cells resulted in a decrease in levels of FOXP3(+) regulatory T cells, this decrease was inhibited by MSC co-transfer. Moreover, MSCs were able to suppress both allogeneic and insulin-specific proliferative responses in vitro. This suppressive effect was associated with the induction of IL10-secreting FOXP3(+) T cells.

CONCLUSIONS/INTERPRETATION

MSCs prevent autoimmune beta cell destruction and subsequent diabetes by inducing regulatory T cells. MSCs may thus offer a novel cell-based approach for the prevention of autoimmune diabetes and for islet cell transplantation.

Contrasting cellular and humoral autoimmunity associated with latent autoimmune diabetes in adults

OBJECTIVE

Diabetes is clinically classified into two types: type 1 (T1D) and type 2 diabetes (T2D). Nevertheless, intermediate forms of diabetes are frequent and difficult to recognize and manage appropriately. In this study, we investigated whether patients with intermediate form of diabetes, here called unclassified diabetes (UD), have beta-cell autoimmune markers.

RESEARCH DESIGN AND METHODS

beta-cell autoimmune markers (beta-cell autoantibodies (aAb), peripheral blood mononuclear cells (PBMC) responsive to five islet proteins, cytokine secretion, and human leukocyte antigen (HLA)-DQB1 genotypes) were analyzed in 50 UD patients, 23 age- and HLA-matched normal control subjects, and 23 classic T2D patients.

RESULTS

We observed that 16 out of 50 (32%) UD patients demonstrated responsive PBMCs, as opposed to 1 out of 23 (5%) age- and HLA-matched normal control subjects, and 0 out of 23 classic T2D patients. Overall, 29 (58%) UD patients had at least one marker of beta-cell autoimmunity (beta-cell aAb and/or PBMC autoreactivity), in association with high-risk HLA genotypes DQB1*0201 and/or DQB1*0302. Moreover, the 13 (26%) UD patients who had beta-cell aAb were not the same as those with PBMC autoreactivity, except for one patient. Patients with PBMC autoreactivity were older at the onset of the disease and had a better residual beta-cell function than those with beta-cell aAb.

CONCLUSIONS

Our data confirm that T-cell autoimmunity can be detected in latent autoimmune diabetes in adults patients. We show an inverse correlation between humoral and cellular beta-cell autoimmunities. Possible protective cellular responses in the patients with beta-cell PBMC autoreactivity could have potential therapeutic implications.

The CXCR4/CXCL12 (SDF-1) signalling pathway protects non-obese diabetic mouse from autoimmune diabetes

Chemokines and their receptors are part of polarized T helper 1 (Th1)- and Th2-mediated immune responses which control trafficking of immunogenic cells to sites of inflammation. The chemokine stromal cell-derived factor-1 CXCL-12 (SDF-1) and its ligand the CXCR4 chemokine receptor are important regulatory elements. CXCR4 is expressed on the surface of CD4(+) T cells, dendritic cells and B lymphocytes. Levels of CXCR4 mRNA were increased in pancreatic lymph nodes (PLNs) of 4-week-old non-obese diabetic (NOD) mice in comparison to Balb/C mice. However, a significant reduction of CXCR4 was noticed at 12 weeks both at the mRNA and protein levels while expression increased in the inflamed islets. The percentage of SDF-1 attracted splenocytes in a transwell chemotaxis assay was significantly increased in NOD versus Balb/c mice. SDF-1 attracted T cells completely abolished the capacity of diabetogenic T cells to transfer diabetes in the recipients of an adoptive cell co-transfer. When T splenocytes from NOD females treated with AMD3100, a specific CXCR4 antagonist, were mixed with diabetogenic T cells during adoptive cell co-transfer experiments, prevalence of diabetes in the recipients rose from 33% to 75% (P < 0.001). This effect was associated with an increase of interferon (IFN)-gamma mRNA and a reduction of interleukin (IL)-4 mRNA levels both in PLNs and isolated islets. AMD3100 also reduced IL-4 and IL-10 production of plate-bound anti-CD3 and anti-CD28-stimulated splenocytes. Immunofluorescence studies indicated that AMD3100 reduced the number of CXCR4(+) and SDF-1 positive cells in the inflamed islets. We can conclude that the CXCL-12/CXCR4 pathway has protective effects against autoimmune diabetes.

Dynamic changes of GAD65 autoantibody epitope specificities in individuals at risk of developing type 1 diabetes

AIMS/HYPOTHESIS

Progression to type 1 diabetes is associated with intramolecular epitope spreading to disease-specific antibody epitopes located in the middle region of glutamic acid decarboxylase 65 (GAD65).

METHODS

The relationship between intramolecular epitope spreading of autoantibodies specific to GAD65 in relation to the risk of developing type 1 diabetes was tested in 22 high-risk individuals and 38 low-risk individuals. We determined the conformational epitopes in this longitudinal study by means of competition experiments using recombinant Fab of four GAD65-specific monoclonal antibodies.

RESULTS

Sera from high-risk children in the preclinical stage recognise a specific combination of GAD65 antibody epitopes located in the middle and the C-terminus of GAD65. High risk of progressing to disease is associated with the emergence of antibodies specific for conformational epitopes at the N-terminus and the middle region. Binding to already established antibody epitopes located in the middle and at the N-terminus increases and shows a significant relation (p=0.005) with HLA, which confers risk of developing diabetes.

CONCLUSIONS/INTERPRETATION

In type 1 diabetes, GAD65 antibodies are initially generated against the middle and C-terminal regions of GAD65. In genetically predisposed subjects the autoimmune response may then undergo intramolecular epitope spreading towards epitopes on the N-terminus and further epitopes located in the middle. These findings clearly demonstrate that the GAD65 autoantibody response in the preclinical stage of type 1 diabetes is dynamic and related to the HLA genotypes that confer risk of diabetes. GAD65-specific Fab should prove useful in predicting progression from islet autoimmunity to clinical onset of type 1 diabetes.

Epitope analysis of GAD65Ab using fusion proteins and rFab

The identification of disease-specific autoantibodies to the 65-kDa isoform of glutamate decarboxylase (GAD65Ab) epitopes in type 1 diabetes has been hampered by their conformational nature. Here, we compared two methods of GAD65Ab epitope analysis: GAD65/67 fusion proteins and competition assays using GAD65-specific recombinant fraction antigen binding (rFab). Sera from newly diagnosed type 1 diabetes patients (n=61) were studied using both approaches. Competition of GAD65 binding by an rFab to a specific epitope did not correlate with binding to the fusion protein that represented this epitope. Conversely, samples that bound to specific fusion proteins were not necessarily competed with rFab specific to determinants in the same region. We conclude that epitopes of different characteristics are detected by fusion proteins and by competition with rFab. Fusion proteins allow the definition of large epitope regions; however, some conformational GAD65Ab epitopes, especially those residing in the middle region, are destroyed or distorted in the fusion proteins. Competition studies using rFab allow the identification of conformational epitopes. However, monoclonal rFab may only reflect a limited proportion of the epitopes recognized by polyclonal sera. A combined analysis using both approaches may therefore be necessary to gain best understanding of autoantibody characteristics and affinity maturation.

Modulation of antigen presentation by autoreactive B cell clones specific for GAD65 from a type I diabetic patient

We used a GAD65-specific human B-T cell line cognate system in vitro to investigate the modulation of GAD65 presentation by autoantibody, assessed in a proliferation assay. Generally, if the T cell determinant overlaps or resides within the antibody epitope, effects of presentation are blunted while if they are distant can lead to potent presentation. For three different autoreactive B-T cell line cognate pairs, the modulation of GAD65 presentation followed the mode of overlapping or distant epitopes with resultant potent or undetectable presentation. However, other cognate pairs elicited variability in this pattern of presentation. Notably, one B cell line, DPC, whose antibody epitope did not overlap with the T cell determinants, was consistently poor in presenting GAD65. Using the fluorescent dye Alexa Fluor 647 conjugated to GAD65 to study receptor-mediated antigen endocytosis showed that all the antigen-specific B cell clones were efficient in intracellular accumulation of the antigen. Additionally, multicolour immunofluorescence microscopy showed that the internalized GAD65/surface IgG complexes were rapidly targeted to a perinuclear compartment in all GAD-specific B cell clones. This analysis also demonstrated that HLA-DM expression was reduced strongly in DPC compared to the stimulatory B cell clones. Thus the capability of antigen-specific B cells to capture and present antigen to human T cell lines is dependent on the spatial relationship of B and T cell epitopes as well other factors which contribute to the efficiency of presentation.

Recombinant Fabs of human monoclonal antibodies specific to the middle epitope of GAD65 inhibit type 1 diabetes-specific GAD65Abs

Autoantibodies to the 65-kDa isoform of GAD (GAD65Abs) are associated with type 1 diabetes development, but the conformational nature of the GAD65Ab epitopes complicates the evaluation of disease risk. Six GAD65-specific recombinant Fabs (rFabs) were cloned from monoclonal antibodies b96.11, DP-C, DP-A, DPD, 144, and 221-442. The binding of GAD65Abs in 61 type 1 diabetic patients to GAD65 was analyzed by competitive radioimmunoassays with the six rFabs to ascertain disease-specific GAD65Ab binding specificities. The median binding was reduced significantly by rFab b96.11 (72%) (P < 0.0001), DP-A (84%) (P < 0.0001), DP-C (84%) (P < 0.0001), 221-442 (79%) (P < 0.0001), and DP-D (80%) (P < 0.0001). The competition pattern in type 1 diabetic patients differed from that in GAD65Ab-positive late autoimmune diabetes in adults (LADA) patients (n = 44), first-degree relatives (n = 38), and healthy individuals (n = 14). Whereas 87 and 72% of the type 1 diabetic sera were competed by rFab b96.11 and DP-C, respectively, only 34 and 26% of LADA patients, 18 and 25% of first-degree relatives, and 7 and 28% of healthy individuals showed competition (P < 0.0001). These findings support the view that type 1 diabetes is associated with disease- and epitope-specific GAD65Abs and supports the notion that the middle epitope is disease associated. These GAD65-specific rFabs should prove useful in predicting type 1 diabetes and in the study of conformational GAD65Ab epitopes.

Reduction of the risk of relapse after withdrawal of medical therapy for Graves' disease

It has been a continuing challenge to try and identify those patients with hyperthyroid Graves' disease likely to remain in remission after an antithyroid drug course or to manage the medical treatment so as to increase the chance of remission. On average, the overall relapse rate is approximately 50% and any significant reduction of this figure would be of practical as well as theoretical value. The numerous controlled prospective studies performed in many parts of the world, with varying iodine intakes, have all confirmed that the main initial features related to the subsequent risk of relapse are: young age, male gender, goiter larger than 40 mL, hypoechogenic and hypervascular gland, high level of anti-thyrotropin receptor antibody (TRAb), detected either with radioreceptor assay (TBII: >40 U/L) or the biologic stimulation assay (thyroid-stimulating antibodies [TSAb]; >300%), severity of hyperthyroidism, and possibly the presence of ophthalmopathy. Alone, each of these has a low predictive value, but together they allow evaluation of the risk of relapse, thus helping treatment choice. As to the modalities of antithyroid drug treatment, dose of the drug or addition of levothyroxine does not affect posttreatment outcome. In contrast, significantly fewer relapses occur for drug courses longer than at least 1 year. Persistence of high levels of TRAb after medical treatment is strongly predictive of relapse but this is of limited value because in most patients, TRAb levels are low or even undetectable at the end of treatment, which does not indicate for further outcome. Smoking is a significant independent risk factor for relapse. In conclusion, reduction of the risk of relapse in patients with medically treated hyperthyroid Graves' disease relies on clinical competence and appropriate management taking into account an array of factors none of which alone has definite predictive value.

Suppressive effect of glutamic acid decarboxylase 65-specific autoimmune B lymphocytes on processing of T cell determinants located within the antibody epitope

Type 1 diabetes is a T cell-mediated disease in which B cells serve critical Ag-presenting functions. In >95% of type 1 diabetic patients the B cell response to the glutamic acid decarboxylase 65 (GAD65) autoantigen is exclusively directed at conformational epitopes residing on the surface of the native molecule. We have examined how the epitope specificity of Ag-presenting autoimmune B cell lines, derived from a type 1 diabetic patient, affects the repertoire of peptides presented to DRB1*0401-restricted T cell hybridomas. The general effect of GAD65-specific B cells was to enhance Ag capture and therefore Ag presentation. The enhancing effect was, however, restricted to T cell determinants located outside the B cell epitope region, because processing/presentation of T cell epitopes located within the autoimmune B cell epitope were suppressed in a dominant fashion. A similar effect was observed when soluble Abs formed immune complexes with GAD65 before uptake and processing by splenocytes. Thus, GAD65-specific B cells and the Abs they secrete appear to modulate the autoimmune T cell repertoire by down-regulating T cell epitopes in an immunodominant area while boosting epitopes in distant or cryptic regions.

Management of fetal thyroid goitres: a report of 11 cases in a single perinatal unit

Fetal thyroid goitres may reveal hormonal imbalance. This can jeopardize neurological development and fetal outcome even when early postnatal treatment is provided. We report a series of 11 goitres diagnosed antenatally in women with past or present thyroid disorders or discovered fortuitously on ultrasound scan. Fetuses presented with hyperthyroidism in three cases and hypothyroidism in eight. Hypothyroidism was iatrogenic in five cases, due to maternal anti-thyroid drugs. Hyperthyroidism was induced by transplacental transfer of thyroid stimulating antibodies (TSHrab). Accurate diagnosis of fetal thyroid status was obtained by fetal blood sampling but this invasive method was deemed necessary only in four cases as maternal clinical and biological data and ultrasound signs provided sufficient information to infer the type of thyroid disorder in the remaining patients. Fetal therapy relied on reduction of maternal antithyroid medication and, in selected cases, intra-amniotic injection of levothyroxin in hypothyroidism, and on administration of antithyroid drugs in hyperthyroidism. All newborns were healthy and none displayed consequences of severe thyroid imbalance. No caesarean section was performed for dystocia. Fetal thyroid goitres can be managed successfully with selected use of invasive diagnostic and therapeutic techniques.

Two amino acids in glutamic acid decarboxylase act in concert for maintenance of conformational determinants recognised by Type I diabetic autoantibodies

AIMS/HYPOTHESIS

Glutamic acid decarboxylase 65 is a major autoantigen in Type I (insulin-dependent) diabetes mellitus, autoimmune polyendocrine syndrome and stiff-man syndrome. These disorders are characterised by the presence of multiple autoantibodies to the autoantigen which can be distinguished in a variety of different ways. We have investigated the role of single amino-acid mutations in glutamic acid decarboxylase 65 in distinguishing the binding of serum antibodies and a variety of patient-derived human IgG monoclonal antibodies directed to different determinants of the autoantigen.

METHODS

We identified a mutant of glutamic acid decarboxylase 65 that contained four single amino-acid mutations from the wild-type molecule. The role of these mutations was investigated by site-directed mutagenesis. We investigated the binding of patient-derived serum antibodies to glutamic acid decarboxylase 65 to a number of single and double amino-acid mutants using immunoprecipitation with labelled, recombinant antigen. To overcome the heterogeneity of different anti-glutamic acid decarboxylase 65 antibodies present in a patient's serum, the binding of a panel of eleven patient-derived human monoclonal antibodies recognising different determinants on the autoantigen was also studied.

RESULTS

Two replacements in glutamic acid decarboxylase 65 at Asn247Ser and Leu574Pro were identified that preferentially influence the anti-glutamic acid decarboxylase 65 serum antibodies of Type I diabetic patients, without statistically significantly effecting those recognised in other disorders. Single or double amino-acid replacements Asn247Ser and Leu574Pro in the autoantigen showed differential affects on expression of epitopes recognised by the human monoclonals. The double replacement of Asn247Ser and Leu574Pro in glutamic acid decarboxylase 65 resulted in the loss of binding of all eleven human monoclonal antibodies, irrespective of their epitope recognition. In contrast, single replacement of Leu574Pro statistically significantly reduced the binding of some carboxyl terminal-directed antibodies such as MICA 1, MICA 3 and DP-A without influencing the binding of other monoclonals. Replacement of Asn247Ser did not, however, influence the binding of any patients serum or human monoclonal antibodies.

CONCLUSION/INTERPRETATION

Two distantly spaced amino acids, Asn247 and Leu574 in glutamic acid decarboxylase 65 were identified that act in concert to greatly influence the conformational structure of the autoantigen and statistically significantly influence the binding of antibodies present in Type I diabetic sera. The single or double amino-acid mutants can be used to distinguish some anti-glutamic acid decarboxylase-65 autoantibodies and could prove useful in distinguishing Type I diabetic from autoimmune polyendocrine syndrome and stiff-man syndrome patients' sera as well as to study changes in antibody patterns during disease progression.

The relationship between peripheral T cell reactivity to insulin, clinical remissions and cytokine production in type 1 (insulin-dependent) diabetes mellitus

Antigenic proliferative responses of peripheral blood mononuclear cells (PBMC) to insulin were studied in 44 type 1 new-onset diabetic subjects. Of them, 14 (32%) had a stimulation index (> or =3) above the mean + 3 SD of 39 healthy controls and of 7 of 15 (47%) diabetic patients of long duration (P = 0.001). Responses to insulin were not dictated by specific major histocompatibility complex class II association and were not observed in normal subjects with diabetes-associated human leukocyte antigen-DR/DQ alleles. Whereas no relation of PBMC reactivity with insulin autoantibodies was found, there was a positive correlation with the presence of at least one of the four autoantibodies tested and with IA-2 antibody. An interesting finding was that the proportion of patients with subsequent low insulin requirement, up to 24 months, was significantly higher in patients who showed PBMC reactivity to insulin (8 of 8) than in those who did not (10 of 24, 42%; P = 0.004). The former had a higher mean stimulation index than the latter (3.3+/-2.6 vs. 1.5+/-0.6; P = 0.006). Furthermore, interleukin-4 (IL-4) production was lower in type 1 diabetic patients who proliferated to insulin than in those who did not (23+/-15 vs. 64+/-47 pg/mL; P = 0.04), but interferon-gamma, IL-2, and IL-10 productions were similar. In conclusion, these results suggest that proliferation to insulin may reflect the presence of an higher residual beta-cell mass.

T cell response pattern to glutamic acid decarboxylase 65 (GAD65) peptides of newly diagnosed type 1 diabetic patients sharing susceptible HLA haplotypes

Autoantibodies and autoreactive T lymphocytes directed against several pancreatic beta cell proteins such as GAD65 have been identified in the circulation before and at the onset of clinical type 1 (insulin-dependent) diabetes. Using GAD65 synthetic peptides, we studied the proliferative response of peripheral blood mononuclear cells (PBMC) either from recently diagnosed type 1 diabetic patients, of whom the majority share the disease-associated HLA class II haplotype (DR4-DQB1*0201 or DR3-DQB1*0302), or from HLA-matched control subjects. We found that 67% (14/21) of the type 1 diabetic patients and 39% (9/23) of the control subjects exhibited a positive proliferative response. Compared with control subjects, however, PBMC from diabetic patients proliferated more frequently (P < 0.05) in the presence of peptide pools from the C-terminal region of GAD65 (amino acids 379-585). Diabetic patients with the same HLA-DQ or HLA-DR alleles showed partially identical T cell reactivity, but no clear correlation could be made between MHC class II specificity and T cell epitopes because of multiple combinations of class II alleles. In addition, by flow cytometry, we studied the direct binding of GAD65 peptides to MHC class II molecules of Epstein-Barr virus (EBV)-transformed B (EBV-B) cells obtained from a diabetic patient. We found that 11 GAD peptides were able to bind to the highly susceptible haplotype DRB1*0301/0401-DQA1*0301/0501-DQB1*0302/0201 on the surface of EBV-B cells in partial correlation with the results obtained in the proliferation assays.

High-resolution autoreactive epitope mapping and structural modeling of the 65 kDa form of human glutamic acid decarboxylase

The smaller isoform of the GABA-synthesizing enzyme, glutamic acid decarboxylase 65 (GAD65), is unusually susceptible to becoming a target of autoimmunity affecting its major sites of expression, GABA-ergic neurons and pancreatic beta-cells. In contrast, a highly homologous isoform, GAD67, is not an autoantigen. We used homolog-scanning mutagenesis to identify GAD65-specific amino acid residues which form autoreactive B-cell epitopes in this molecule. Detailed mapping of 13 conformational epitopes, recognized by human monoclonal antibodies derived from patients, together with two and three-dimensional structure prediction led to a model of the GAD65 dimer. GAD65 has structural similarities to ornithine decarboxylase in the pyridoxal-5'-phosphate-binding middle domain (residues 201-460) and to dialkylglycine decarboxylase in the C-terminal domain (residues 461-585). Six distinct conformational and one linear epitopes cluster on the hydrophilic face of three amphipathic alpha-helices in exons 14-16 in the C-terminal domain. Two of those epitopes also require amino acids in exon 4 in the N-terminal domain. Two distinct epitopes reside entirely in the N-terminal domain. In the middle domain, four distinct conformational epitopes cluster on a charged patch formed by amino acids from three alpha-helices away from the active site, and a fifth epitope resides at the back of the pyridoxal 5'-phosphate binding site and involves amino acid residues in exons 6 and 11-12. The epitopes localize to multiple hydrophilic patches, several of which also harbor DR*0401-restricted T-cell epitopes, and cover most of the surface of the protein. The results reveal a remarkable spectrum of human autoreactivity to GAD65, targeting almost the entire surface, and suggest that native folded GAD65 is the immunogen for autoreactive B-cells.

Peptide specificity of high-titer anti-glutamic acid decarboxylase (GAD)65 autoantibodies

To study systematically the linear epitope specificity of anti-glutamic acid decarboxylase (GAD) autoantibodies associated with insulin-dependent diabetes mellitus (IDDM), we produced 93 overlapping 12-residue synthetic peptides derived from the sequence of the human GAD65 protein and covering the entire length of the protein. These peptides were used as antigens in an enzyme immunoassay to screen the sera from 10 IDDM patients, all of which contained at high level autoantibodies directed against GAD65. Three out of ten (30%) IDDM patients had antibodies that reacted with one or more of the synthetic peptides. Two of the peptide-reactive IDDM sera, which also bound denatured recombinant GAD65 on western blots, had the highest titers of anti-GAD antibodies in ELISA assay. Moreover, the anti-GAD antibodies-GAD complexes formed with these sera were characterized by low dissociation rates, indicative of their good stability. A fine specificity analysis, using analogs of antigen peptide 1 (residues 1-12), allowed us to identify the residues at positions 5-9 (GSGFW) as critical for antibody recognition.

Antibody-dependent cell-mediated cytotoxicity in autoimmune thyroid disease: relationship to antithyroperoxidase antibodies

Thyroid antibody-dependent cell-mediated cytotoxicity (ADCC) has been reported in autoimmune thyroid disease, and its relationship with antithyroperoxidase antibodies (TPOAb) questioned. We studied the effect of highly purified human thyroperoxidase (TPO) on thyroid ADCC activity elicited by serum from patients with autoimmune thyroid disease. ADCC promoted by a pool of Graves' disease sera could be inhibited by the addition of TPO in a dose-dependent manner. TPO at 40 micrograms/mL decreased the ADCC observed in the presence of this serum pool by 50%. In the presence of 40 micrograms/mL TPO, ADCC was significantly reduced (P < 0.0005) from 39.6 +/- 10.6% (mean +/- SD) to 14.0 +/- 12.9% for the 18 Graves' disease sera tested and from 39.1 +/- 10.5% to 6.1 +/- 1.7% for the 16 thyroiditis sera tested. Purified thyroglobulin had no effect. Immunoaffinity-purified TPOAb could mediate ADCC in a dose-dependent manner, whereas purified antithyroglobulin antibodies could not. Three TPOAb-positive, but ADCC-negative, sera appear to contain an activity able to protect thyroid cells from ADCC. This protective effect is also observed on human fibroblasts. In conclusion, TPO is the major antigen involved in thyroid ADCC.

Four IgG anti-islet human monoclonal antibodies isolated from a type 1 diabetes patient recognize distinct epitopes of glutamic acid decarboxylase 65 and are somatically mutated

The selective destruction by an autoimmune process of the beta cells in the pancreas is the hallmark of the type 1 insulin-dependent diabetes mellitus. What triggers islet cell-specific autoreactive T and B cells, however, remains unclear. Identification of the targets of the anti-islet cell autoantibodies frequently found in insulin-dependent diabetes mellitus patients and analysis of their sequences should provide some insights into the nature of this disease. We have combined EBV transformation with CD40 activation of peripheral B cells from one patient with insulin-dependent diabetes mellitus to isolate four B cell clones that secrete islet cell-specific autoantibodies, These four human monoclonal autoantibodies are of the IgG1 isotype, and they each recognize a different epitope of the glutamic acid decarboxylase enzyme. Analysis of their variable gene sequences shows that, while clonally unrelated, three of the four human monoclonal autoantibodies use a member of the VH4 family, and two have rearranged the same delta light chain variable gene. The IgG1 isotype of the four autoantibodies as well as the presence of somatic mutations in both heavy and light chain genes provide concrete evidence for their derivation by a T cell-dependent immune response.

Four IgG anti-islet human monoclonal antibodies isolated from a type 1 diabetes patient recognize distinct epitopes of glutamic acid decarboxylase 65 and are somatically mutated

The selective destruction by an autoimmune process of the beta cells in the pancreas is the hallmark of the type 1 insulin-dependent diabetes mellitus. What triggers islet cell-specific autoreactive T and B cells, however, remains unclear. Identification of the targets of the anti-islet cell autoantibodies frequently found in insulin-dependent diabetes mellitus patients and analysis of their sequences should provide some insights into the nature of this disease. We have combined EBV transformation with CD40 activation of peripheral B cells from one patient with insulin-dependent diabetes mellitus to isolate four B cell clones that secrete islet cell-specific autoantibodies, These four human monoclonal autoantibodies are of the IgG1 isotype, and they each recognize a different epitope of the glutamic acid decarboxylase enzyme. Analysis of their variable gene sequences shows that, while clonally unrelated, three of the four human monoclonal autoantibodies use a member of the VH4 family, and two have rearranged the same delta light chain variable gene. The IgG1 isotype of the four autoantibodies as well as the presence of somatic mutations in both heavy and light chain genes provide concrete evidence for their derivation by a T cell-dependent immune response.

[Thyroid-stimulating hormone receptor and thyroid diseases]

Since the description of the structure of the TSH receptor using molecular biology techniques, it has become possible to analyse the role of anomalies of this receptor in thyroid disorders. Implicated in the pathophysiology of Graves' disease by indirect observations, the autoantigenic role of the TSH receptor has now been clearly confirmed. Nevertheless, the epitopes of the extracellular domain of the receptor corresponding to each type, stimulatory or epitopes of the extracellular domain of the receptor corresponding to each type, stimulatory or blocking, of anti-receptor toward activation or blocking. The events that induce and maintain autoimmunization to the receptor remain hypothetical, but the possible existence of soluble forms of the receptor opens new perspectives. In practice, however, assessment of TSH anti-receptor antibodies is useful in managing Graves' disease and in certain cases of primary myxoedema linked to the presence of blocking antibodies; it is mandatory in pregnant women for detection of foetal disease induced by maternal antibodies. The responsibility of the receptor is sought in other thyroid diseases such as toxic adenoma, rare forms of nonimmunologic, familial hyperthyroidism, simple goiter, nodules and lack of response to TSH. Recently, a mutation mapped into the 3rd intracellular loop has been shown in toxic adenoma. Such discoveries are as important for physicians (and patients) as for cellular biologists.

Assessment of antibody dependent cell cytotoxicity in autoimmune thyroid disease using porcine thyroid cells

Antibody Dependent Cell Cytotoxicity (ADCC) appears to be involved in Autoimmune Thyroid Disease (AITD). Homologous system may trigger non-specific reactions which might obscure specific ADCC. Heterologous target cells may be useful for studying ADCC, provided relevant antigen(s) are expressed. We therefore tested the capacity of porcine thyroid cells to elicit ADCC reaction in the presence of sera from various patients with AITD. Porcine thyroid cells were used in a 4-hr chromium release assay in the presence of 1/10 heat inactivated human sera and human peripheral blood lymphocytes at a 30:1 effector-target ratio. There was a significant correlation (r = 0.64; P < 0.01) between ADCC activities tested on human or porcine thyroid cells. Serum or IgG effects on porcine thyroid ADCC were dose-dependent between 1/10 to 1/10,000 dilutions. Non-thyroid cell systems were unaffected by thyroid cytotoxic sera. Porcine thyrocyte susceptibility to ADCC peaked at the fourth day of culture and was enhanced by addition of TSH or TSH and methimazole in the culture medium. Using this heterologous system, we demonstrated ADCC activity in a significant proportion of patients with thyroiditis (14/19), Graves' opthalmopathy (19/44) or of mothers of children with congenital hypothyroidism (14/39) and in the children themselves (15/39). Discrepancies observed in some sera between ADCC activity and antithyroperoxidase antibody suggest that thyroperoxidase is not the only antigen involved in ADCC. These results indicate that porcine thyroid cells appear suitable for ADCC assay in patients with AITD. Also this system should be helpful to characterize the antigen-antibody involved.

[Synthetic antithyroid drugs and Basedow's disease or the choice of a therapeutic strategy]

We present the conclusions of two prospective studies of patients examined at their first manifestation of Graves' disease and treated with antithyroid drugs (ATD). The purpose of the first study was to investigate the effects of long-term treatment: the patients were given carbimazole in degressive doses without hormone replacement for 18 months, the followed up for 2 to 6 years after drug withdrawal. The second study was designed to determine the effect of treatment duration on the prognosis: the patients were given an ATD according to the same protocol for a duration randomly set at either 6 or 18 months, then seen again 2 years after ATD withdrawal. The results showed that after 18 months of treatment at least 50 percent of the patients could be expected to remain in remission for 6 years. Remissions were less frequent when treatment was shorter (41.7 percent after the 6 month treatment versus 61.8 percent after the 18 month treatment, with a 2 years' follow-up; P less than 0.05). The relapses that occurred came early: 70 percent of them took place within the first post-treatment month. This article also provides evidence of high T3 and/or T4 levels without signs of thyrotoxicosis during the post-treatment clinical course; these exclusively biochemical relapses spontaneously disappeared and may have been expressing epidoses of active thyroiditis.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti TSH-receptor antibodies in pregnant patients with autoimmune thyroid disorder

The study was designed to test further the usefulness of the radioreceptor assay of thyroid stimulating hormone (TSH) binding inhibitory immunoglobulins (TBII) and the bioassay of thyroid stimulating antibodies (TSAb) or TSH stimulated cAMP response inhibitory antibodies (TBkAb) in the prediction of neonatal thyroid dysfunction. Of 63 pregnant women with a current or past history of autoimmune thyroid disorder, 11 (one with active and six with a past history of Graves' disease and four with autoimmune thyroiditis) gave birth to a baby with transient hyper or hypo-thyroidism. Only high maternal titres (which could persist after partial thyroidectomy) of anti TSH-receptor antibodies (TRAb) led to neonatal hyperthyroidism. Both types of assay were able to detect the antibodies responsible for transitory neonatal autoimmune thyroid disease. TBII values reflected TSAb titres so that there was a significant correlation between the results of both assays in women with Graves' disease and in neonatal sera. Positive TBII and TBkAb activities were present in 5 of the 28 women with autoimmune thyroiditis. Therefore, when TBII is positive, the functional characterization of the antibodies warrants the use of the bioassay.

Antithyroid drugs and Graves' disease: a prospective randomized evaluation of the efficacy of treatment duration

A prospective randomized study was performed in patients with hyperthyroid Graves' disease (GD) in order to compare long (18 months) and short term (6 months) antithyroid drug treatment on the remission rate. A therapeutic protocol was offered to all GD patients who had not been treated for this disease previously. All patients studied who followed the protocol were rechecked 2 yr after treatment was withdrawn, or earlier in the case of relapse. Of the patients having undergone long term treatment, 61.8% still were in remission 2 yr after treatment withdrawal, whereas only 41.7% of the patients treated for 6 months were in remission (P less than 0.05). Such findings clearly establish that treatment duration has a direct beneficial incidence on the remission rate. These results were confirmed by the fact that treatment for 18 months resulted in remission in 7 of 15 patients who had previously relapsed after a 6-month course of therapy. This improvement in relation to treatment duration might be due to the immunosuppressive action of carbimazole. No significant difference was observed between relapse and remission groups, regardless of treatment duration, for HLA ABDr, serum T3 and T4, and T3/T4 ratio determined before treatment. Only the thyroid-stimulating antibody levels determined at the time of diagnosis and at the end of treatment were higher in the relapse group, a difference that was relevant only globally, due to value scattering. Furthermore, thyroid-stimulating antibody levels at the end of treatment may indicate remission or, conversely, continuance of the pathological process.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for several cell populations in human thyroid with distinct glycosphingolipid patterns

Thyrocytes, which are functional cells of human thyroid, have been isolated, and their glycosphingolipid content has been analyzed in the various fractions obtained from the digested gland as well as in the tissue remaining after enzymatic treatment. The ganglioside content was not significantly different in the different fractions, with GM3 and Gd3 as major components. Analysis of neutral glycolipids revealed striking differences between isolated thyrocytes and whole thyroid. The membraneous material released from the proteinase-treated thyroid presented a pattern of monohexosylceramides clearly distinct from that of thyrocytes. The present data suggest the presence of at least two cellular populations with distinct glycolipid patterns in thyroid tissue: accessory cells containing most of the glycolipids, and thyrocytes in which the major neutral glycosphingolipid is phytosphingosine-containing glucosylceramide.

Blocking anti-thyrotropin receptor antibodies desensitize cultured human thyroid cells

Stimulating anti-TSH receptor antibodies (TSAb) mimic TSH in the induction of refractoriness in cultured thyroid cells; TSAb and TSH desensitize one another. We investigated whether blocking anti-TSH receptor antibodies (TBkAb) have the same desensitizing effects in cultured human thyroid cells. Prolonged exposure of cells (20 h) to TBkAb followed by antigen-antibody dissociation by an acid wash step was required to induce refractoriness to subsequent stimulation of cAMP accumulation with TSH and TSAb. Cycloheximide prevented this desensitization effect. The cAMP response to forskolin was not reduced in cells pretreated by TBkAb and was increased in cells desensitized by TSH or TSAb. The pattern of the TSH dose-response curves suggested that desensitization by TSH or TSAb involved only a postreceptor mechanism but both receptor and postreceptor phenomena in the case of TBkAb. In conclusion, like TSH or TSAb, TBkAb may induce a homologous desensitization in human thyroid cells which is not mediated by cAMP.

Monoclonal antibody approach to the relationship between immunological structure and biological activity of thyrotropin

In order to locate the domains involved in the biological activity of TSH and to get some insight in the relationship between immunological and biological properties of TSH, 24 monoclonal antibodies (mAb) to 11 different antigenic regions of hTSH were tested for both binding to hTSH and inhibition of hTSH stimulation of adenylate cyclase in human thyroid membranes. These mAb were also investigated for binding to bovine TSH (bTSH), and interference with bTSH binding to the receptor and stimulation of adenylate cyclase. Radioiodinated human TSH (hTSH) was incubated with increasing concentrations of mAb. Maximum hTSH binding by the various mAb ranged from 15-75% and was not related to the apparent affinity of the mAb for hTSH. Maximum inhibition by the mAb of hTSH stimulation of adenylate cyclase ranged from 3-92%. As compared to the antigenic map of hTSH, it was observed that mAb reacting with the same antigenic regions might display varying inhibition of hTSH. Nevertheless, it was clearly shown that the most potent inhibitors of hTSH stimulatory activity interacted with epitopes located on the alpha- and beta-subunits or expressed only by holo hTSH. Only 11 of the 24 mAb cross-reacted significantly with bTSH. Seven exhibited the same inhibition of hTSH and bTSH stimulatory activity; the four remaining mAb rather than to inhibit adenylate cyclase stimulation as observed with hTSH, did not interfere or even increased adenylate cyclase stimulation by bTSH.(ABSTRACT TRUNCATED AT 250 WORDS)

Thyroid stimulating antibody: an index of thyroid stimulation in Graves' disease?

Early (20 min) thyroid radio-iodine uptake (ERU) and thyroid-stimulating antibodies (TSab) were determined in 27 untreated unselected patients with Graves' disease at the time of diagnosis. In 21 subjects the same tests were further performed in parallel during combined carbimazole-L-T3 therapy (mean duration of follow-up: 10.8 +/- 5.8 months; mean +/- SD). TSab was determined by a cAMP-human thyrocyte culture stimulation assay and expressed in microliter-equivalent of a TSab standard/ml (microliter-eq/ml). Before treatment, ERU, ranging from 15 to 54% of the injected dose (normal less than or equal to 8% dose) correlated with serum T3 (r: 0.54; P less than 0.01); TSab, ranging from 6 to 85 microliter-eq/ml was detected in 21/27 patients. There was a significant correlation between ERU and TSab (Spearman rank test: r: 0.57; P less than 0.01). During the first months of treatment, 5 of the 21 patients sequentially studied had undetectable TSab levels throughout the study and in these patients ERU decreased by 57% of its initial value; the remaining 16 subjects were divided into two groups according to ERU changes: in group A (9 patients), initial ERU decreased by 50% or more or the absolute value became less than 20% of the dose and TSab decreased from 10.9 +/- 4.8 microliter-eq/ml to 5.3 +/- 1.6 microliter-eq/ml (P less than 0.01); in group B (7 patients), the fall of ERU was less than 50% or the absolute value remained greater than 20% of the dose and TSab values remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

[Biological criteria of isolated Graves' ophthalmopathy]

The diagnostic value of biological tests, especially the thyroid stimulating immunoglobulin (TSI) assay, was studied in 29 patients with endocrine Graves' ophthalmopathy without hyperthyroidism. In 21 patients the presence of biological abnormalities (L-T3 suppression test, TRH test, presence of antithyroid antibodies) indicated that the ophthalmopathy was related to Graves' disease. The remaining 8 patients were free of any biological abnormality. The contribution of the TSI assay to the pathophysiological diagnosis of ophthalmopathy is poor. These immunoglobulins were detected in 12 out of 29 cases, but they were associated with the above-mentioned abnormalities in all but 3 of these 12 cases.

Immunological parameters in Graves' disease: are they useful for indication and monitoring of antithyroid drug treatment?

This paper reviews the available published data on studies of a correlation between the presence or intensity of measurable immunological abnormalities or markers in Graves' disease and the outcome after a course of antithyroid drug. The following parameters are discussed: circulating anti-thyroid-stimulating hormone receptor antibodies; antitubulin antibodies; human lymphocyte antigens, and repartition of T-lymphocyte subsets. At the present time no single parameter has any real practical value for individual patients either to indicate or monitor antithyroid drug therapy. The more useful information remains the anti-thyroid-stimulating hormone receptor level at the end of treatment which, if elevated, is predictive of relapse. Several areas of research, however, appear promising.

T lymphocyte subsets at various stages of hyperthyroid Graves' disease: effect of carbimazole treatment and relationship with thyroid-stimulating antibody levels or HLA status

Markers of autoimmunity in hyperthyroid Graves' disease were studied at various stages of the disease in connection with HLA status. The 148 patients studied were included in a long term prospective evaluation of antithyroid drug treatment. The proportions of total T lymphocytes and OKT4 and OKT8 positive cells in peripheral blood and circulating thyroid-stimulating antibodies were determined before treatment (M0; 46 patients), after 6 (M6; 50 patients), and 18 months (M18; 22 patients) of carbimazole treatment, at relapse (15 patients) and after 2 yr of euthyroidism after drug withdrawal (remission; 23 patients). Twenty-seven patients were sequentially studied between M0 and M6, and M6 and M18. As compared to matched normal subjects, the mean proportion of OKT8 positive cells was significantly decreased in every group of patients, even in those in remission, and the mean OKT4/OKT8 cell ratios were increased in all groups except the patients in remission. However, OKT4/OKT8 cell ratios in individual M0 patients were widely distributed, being normal in 50%. No correlation was found between the proportions of T cell subsets and thyroid-stimulating antibody values, and the two measures varied independently in patients studied sequentially. OKT8 lymphocyte subset was dependent on HLA status. In DR3-positive patients, the mean OKT4/OKT8 cell ratio was high at all stages of the study; in DR3-negative patients it decreased significantly at M18 and was normal in those patients who had a remission. However, in the DR3-positive and -negative groups of patients, the mean OKT4/OKT8 ratios at M0 and at relapse were similar. In conclusion, the proportions of circulating OKT8 positive lymphocytes reflect only poorly the activity of the immune abnormalities in Graves' disease, but do correlate with HLA-DR3 status.

Thyroid stimulating antibodies: an aid to the strategy of treatment of Graves' disease?

In 1976 we initiated a prospective study to specify the usefulness of thyroid stimulating antibody (TSAb) determinations in predicting the outcome of post-antithyroid drug treatment for Graves' disease. This study was carried out on 55 patients, who were either treated for six (n = 16) or 18 months (n = 39) and followed up for an additional two-year period. TSAb was determined on whole serum in 29 patients before and at the end of treatment, and in 26 patients at the end of treatment only. These determinations were carried out using a sensitive and reproducible microassay based on cAMP accumulation in human thyroid cell cultures. Before treatment, TSAb ranging from 170 to 1529% was present in 28/29 patients and reached significantly low levels at the end of treatment whatever its duration. TSAb was undetectable in 24/55 patients at the end of treatment. 8/16 'short-treated' and 18/39 'long-treated' patients remained in remission. As expected, initial TSAb levels had no predictive value. End-treatment TSAb values, when low (less than 350%) or negative did not correlate with later evolution: in these 39 patients, relapse rate was 41%. In contrast, 13/16 patients with end-treatment TSAb greater than 350% relapsed. Relapses tended to occur earlier in patients with the highest TSAb levels. TSAb determined again during follow-up was negative in each of the 18 patients in remission, and positive in 8/10 patients at the time of relapse, whatever its level at the end of the drug course. This study confirms that only end-treatment TSAb levels are predictive of relapse.(ABSTRACT TRUNCATED AT 250 WORDS)